1. Field of the Invention
The present invention is directed to a method for constructing an integrated artificial human tissue construct system and, in particular, construction of an integrated human immune system for in vitro testing of vaccines, adjuvants, immunotherapy candidates, cosmetics, drugs, biologics, and other chemicals. The artificial immune system is useful for assessing the interaction of substances with the immune system, and thus can be used to accelerate and improve the accuracy and predictability of vaccine, drug, biologic, immunotherapy, cosmetic, and chemical development.
2. Background of the Technology
The development and biological testing of human vaccines has traditionally relied on small animal models (e.g., mouse and rabbit models) and then non-human primate models.
The mammalian immune system uses two general adaptive mechanisms to protect the body against environmental pathogens. When a pathogen-derived molecule is encountered, the immune response becomes activated to ensure protection against that pathogenic organism.
The first immune system mechanism is the non-specific (or innate) inflammatory response. The innate immune system appears to recognize specific molecules that are present on pathogens but not on the body itself.
The second immune system mechanism is the specific or acquired (or adaptive) immune response. Innate responses are fundamentally the same for each injury or infection; in contrast, acquired responses are custom-tailored to the pathogen in question. The acquired immune system involves a specific immunoglobulin (antibody) response to many different molecules present in the pathogen, called antigens. In addition, a large repertoire of T cell receptors (TCR) is sampled for their ability to bind processed forms of the antigens bound to major histocompatibility complex (MHC, also known as human leukocyte antigen, HLA) class I and II proteins on the surface of antigen-presenting cells (APCs), such as dendritic cells (DCs).
The immune system recognizes and responds to structural differences between self and non-self proteins. Proteins that the immune system recognizes as non-self are referred to as antigens. Pathogens typically express large numbers of highly complex antigens.
Acquired immunity is mediated by specialized immune cells called B and T lymphocytes (or simply B and T cells). Acquired immunity has specific memory for antigenic structures; repeated exposure to the same antigen increases the response, which increases the level of induced protection against that particular pathogen.
B cells produce and mediate their functions through the actions of antibodies. B cell-dependent immune responses are referred to as “humoral immunity,” because antibodies are found in body fluids.
T cell-dependent immune responses are referred to as “cell mediated immunity,” because effector activities are mediated directly by the local actions of effector T cells. The local actions of effector T cells are amplified through synergistic interactions between T cells and secondary effector cells, such as activated macrophages. The result is that the pathogen is killed and prevented from causing diseases.
Similar to pathogens, vaccines function by initiating an innate immune response at the vaccination site and activating antigen-specific T and B cells that can give rise to long term memory cells in secondary lymphoid tissues. The precise interactions of the vaccine with cells at the vaccination site and with T and B cells of the lymphoid tissues are important to the ultimate success of the vaccine.
Almost all vaccines to infectious organisms were and continue to be developed through the classical approach of generating an attenuated or inactivated pathogen as the vaccine itself. This approach, however, fails to take advantage of the recent explosion in our mechanistic understanding of immunity. Rather, it remains an empirical approach that consists of making variants of the pathogen and testing them for efficacy in non-human animal models.
Advances in the design, creation and testing of more sophisticated vaccines have been stalled for several reasons. First, only a small number of vaccines can be tested in humans, because, understandably, there is little societal tolerance for harmful side effects in healthy people, especially children, exposed to experimental vaccines. With the exception of cancer vaccine trials, this greatly limits the innovation that can be allowed in the real world of human clinical trials. Second, it remains challenging to predict which epitopes are optimal for induction of immunodominant CD4 and CD8 T cell responses and neutralizing B cell responses. Third, small animal testing, followed by primate trials, has been the mainstay of vaccine development; such approaches are limited by intrinsic differences between human and non-human species, and ethical and cost considerations that restrict the use of non-human primates. Consequently, there is a slow translation of basic knowledge to the clinic, but equally important, a slow advance in the understanding of human immunity in vivo.
The artificial immune system (AIS) of the present invention can be used to address this inability to test many novel vaccines in human trials by instead using human tissues and cells in vitro. The AIS enables rapid vaccine assessment in an in vitro model of human immunity. The AIS provides an additional model for testing vaccines in addition to the currently used animal models.
Attempts have been made in modulating the immune system. See, for example, U.S. Pat. No. 6,835,550 B1, U.S. Pat. No. 5,008,116, Suematsu et al., [Nat. Biotechnol., 22, 1539-1545, (2004)] and U.S. Patent Publication No. 2003/0109042. Nevertheless, none of these publications describe or suggest an artificial immune system, which comprises a vaccine site (VS), lymphoid tissue equivalent (LTE), and the use of an AIS for assessing the interaction of substances with the immune system.